Most of the dosimetry work that is carried out at REB has direct or indirect applications to the assessment of radiation doses from bioterrorism events involving environmental radiation. Since 2005, all of the bioterrorism-related studies at REB are funded under an Inter-Agency Agreement between NIAID and NCI. BIODOSIMETRY Analysis of stable chromosome aberrations: Biological monitoring of radiation dose can contribute important, independent estimates of radiation exposure for individuals and populations, especially when physical measurements of radiation exposure are unavailable. Stable chromosome aberrations (SCA) or translocations have been the most widely applied biodosimetry in epidemiologic studies of radiation exposure, because of well-characterized radiation dose-response curves and the persistence of translocations that can be detected many years after radiation exposure. The goal was to establish baseline levels of chromosome translocation frequencies by age, gender, ethnicity and smoking status in unexposed populations. Labratories both in the US and internantionally were contacted that had reported data on translocation frequencies in normal persons using FISH. Translocation data on 1,957 unexposed individuals, were collected and analyzed. Relationships of translocation frequency by age and smoking status were determined. Optically stimulated luminescence (OSL) and human tooth enamel for retrospective dose estimation: REB and collaborators are developing an alternative technique for in vivo retrospective estimation of radiation doses of individuals exposed to ionizing radiation in radiological or nuclear accidents and terrorist attacks. This technique is based on the Optically Stimulated Luminescence (OSL) signal of human dental enamel. More than 100 teeth have been collected from the NIDCR and many measurements made to establish viability of technique and establish approximate limits of detection of a few hundred mGy. Development of refinements are underway. RADIONUCLIDES Radionuclide Studies: Analysis of 131I biokinetic data for hyperthyroid patients: This study is designed to quantitatively analyze biokinetic data on the movement of Iodine-131 (131I) within the human body in more than 3,000 patients who were originally treated with radioactive iodine for thyrotoxicosis prior to 1961, and who were enrolled in the original Thyrotoxicosis Follow-up Health Study (TTFUS). Development of a robust biokinetic model for iodine was completed and the parameters of the biokinetic model and the organ dose coefficients were calculated for the group of 143 patients with iodine measurements in thyroid, iodide, and protein-bound iodine (PBI). Dose estimation was extrapolated for entire cohort. A software tool, KinDose (Kinetic Data Dose Estimation Software) was developed to calculate organ doses from biokinetic measurements of radioactivity in the body when the data are analyzed with the SAAM II simulation and modeling software. RADIOACTIVE FALLOUT Archival of historical documents on worldwide fallout and development of a database to improve fallout prediction models. REB and collaborators develops the first comprehensive database of worldwide fallout data as an accessible research tool containing scanned and searchable historical document collection obtained from the Environmental Measurements Laboratory (EML) for data on fallout deposition worldwide. Using this database REB investigators are developing improved models of local and global fallout dispersion useful for predicting deposition in the event of future nuclear weapons explosions. Study of thyroid nodules and disorders related to exposure to radioactive fallout in Kazakhstan. The REB is conducting an investigation to estimate internal and external radiation dose among persons exposed as children to radioactive fallout from above ground nuclear tests conducted at the Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan between 1949 and 1962. The dosimetry effort is a critical component of a study evaluating the association between radiation exposure and the risk of thyroid disease using U.S./Russian joint dosimetry methodology, the two-dimensional Monte Carlo (2DMC) strategy for dose estimation with uncertainty, and focus group interview strategy for collection of data on individual consumption rates and other behaviors. Marshall Islands, dose and cancer risk assessment. As mandated by Congress, the assessment of radiation doses and risks from nuclear tests conducted in the Marshall Islands was completed. In addition, an estimation of the baseline rate of cancers among the Marshallese population was made and a projection of cancers (thyroid, stomach, colon, red bone marrow) expected as a result of exposure was completed. An analysis of radiation doses received by the U.S. population including Native Americans by the TRINITY nuclear test.) As mandated by Congress, the assessment of doses and risks from the first nuclear test conducted in New Mexico in July 1945 has been partially conducted. Preliminary dose calculations (whole body and thyroid) have been made for residents of New Mexico from TRININTY ,the first nuclear test,New Mexico in July 1945. Web-based fallout dose and risk calculator. As recommended by the National Academies of Science, the estimation of the thyroid radiation doses received by the American people as a result of I-131 in fallout from nuclear weapons tests conducted worldwide is underway including the preparation of a web-based calculator for estimating the corresponding individual thyroid radiation doses and the related thyroid cancer risk. EVALUATION OF CONSEQUENCES OF RADIATION ACCIDENTS (Chornobyl accident) External exposure study (clean-up workers) Within the framework of the second phase of the Chornobyl leukemia study, all interviews were conducted and all bone-marrow doses were reconstructed. Internal exposure study (members of the public) Analysis is almost completed for the epidemiological studies of thyroid cancer among twenty five thousand Ukrainian and Belarusian individuals who were exposed as children at the time of the Chornobyl accident. The thyroid doses resulting from intakes of 131I, which contribute about 95% of the thyroid dose from all pathways of exposure, have been reanalyzed. In Ukraine, a detailed assessment of the uncertainties, in which shared and unshared components are separated, has been performed. In Belarus: (1) the assessment of the age- and region-dependent thyroid masses;(2) the environmental radiation measurements that were collected in Belarus during the two months following the accident;(3) the assessment of the contribution of external and internal contaminations of the body to the signal read by the radiation devices used for the direct thyroid measurements;and (4) the thyroid dose estimates from intakes of 131I.